The present invention relates to systems and methods of generating an oxygen-enriched gas stream from atmospheric air for delivery to the passengers and crew of an aircraft.
Oxygen concentrators on board aircraft, generally referred to by the acronym OBOGS, conventionally employ pressure swing adsorption (PSA or VPSA) processes that use adsorbents capable of separating the constituents of air.
It is known to use for this purpose adsorbents of the zeolite X or zeolite A type that have a high affinity for nitrogen and are therefore capable of delivering an oxygen-enriched mixture, but only up to a content not exceeding, at best, 95% because of the argon content present in the atmospheric air.
To deliver oxygen with a content greater than 95%, it has been proposed, for example in U.S. Pat. No. 4,566,881 (BWV), to use adsorbers in cascade, in arrangements that are ill-suited for onboard applications owing to their size, weight and circuit complexity.
Moreover, zeolites exchanged with silver cations have been known for a long time (cf. U.S. Pat. No. 3,331,190, Dow Chemical), which make it possible in particular to improve the separation of oxygen from nitrogen (cf. WO-A-00/40332, University of Michigan) or to separate argon from oxygen (cf. WO-A-94/06541, Arbor Research Corp.). However, there has been no suggestion as to the possible use of such adsorbents in OBOGS concentrators.